Paul urged his readers to live unbound to the Law of Moses (5:1-12). He also warned them against using their liberty as a license to sin to prevent them from overreacting.
"The theme of love . . . informs all of Paul's exhortations vis-à-vis the Galatians' libertine tendencies . . .
"Yet undergirding all of Paul's admonitions regarding love and service is the reality of life lived by the Spirit,' with references to the Spirit being more frequent in 5:13-6:10 than references to either love or service."179
5:13-14 The "flesh"is the sinful human nature that every person, saved or unsaved, possesses. It is possible to conclude that since it is unnecessary to keep the Law to be saved, it is unnecessary to pay attention to the Law for any reason. However, Paul was not urging his converts to burn their Old Testaments. The Law has values, as he previously pointed out, one of which is to reveal how to express love for God and other people. Really the whole Law is a revelation of how to love (Lev. 19:18; cf. Mark 12:28-31). Under grace we are free to fulfill the Law by loving one another. For the Christian the Mosaic Law has revelatoryvalue (2 Tim. 3:16-17) even though it does not have regulatoryvalue, controlling our behavior.180
If his readers insisted on living in slavery, Paul wished they would enslave themselves to love of one another. If they wanted to live under law, let it be the law of Christ (6:2) impelled by the indwelling Spirit rather than by an external code.
There is no external entity that can enable us to love our neighbors as ourselves, but the Holy Spirit can produce that love within us.
In what sense does Leviticus 19:18 fulfill the whole Mosaic Law?
"There is a play on two meanings of the Greek word peplerotai, translated summed up' [NIV, or fulfilled, NASB]. On the one hand, it refers to the fact that the law can aptly be summarized by the words of Leviticus 19:18. This idea was a commonplace of rabbinic opinion and Jesus endorsed it in Matthew 22:39 and Luke 10:25-28. On the other hand, the word can also mean fulfilled' (as in Rom 13:8), and in this sense Paul is suggesting that it is actually out of the new life of love made possible within the Christian community through the Spirit that the law finds fulfillment."181
". . . the primary meaning is not that we must properly love ourselves before we can love others (although this is true in itself), but that we are to love our neighbor with the same spontaneity and alacrity with which we love ourselves.182
5:15 Apparently the believers who advocated grace and the believers who advocated law bitterly opposed one another in the Galatian churches. Paul cautioned both sides to love one another or they would consume each other. That would not be a good example of Christian love. This is the only sin Paul warned the Galatians to avoid. They were better off spiritually than some other congregations to which he wrote, or possibly he did not want to deal with other needs of theirs in this letter.